EWSR1 and Ewing sarcoma: Finally, 13 ‘unclassifiable' neoplasms which did not show typical histologic or immunohistochemical features of Ewing sarcoma showed EWSR1 rearrangement with FISH but no identifiable partner, that is, they did not harbour detectable EWSR1-related fusion transcripts with the primers available (Table 5) (Figure 2).